In semiconductor devices, the n-type region and the p-type region each need to be brought into low resistance contact with a metal. In the case of an element based on silicon (Si), the sum of the barriers between the n-type region and the p-type region on one hand and the same metal on the other is equal to the magnitude of the band gap, which is approximately 1 electron volt (eV). In this case, by increasing the concentration of dopants in both regions, a sufficiently low contact resistance is obtained. That is, in a Si-based element, the barrier is sufficiently low, and the dopant can be sufficiently introduced and activated.
In the case of an element based on silicon carbide (SiC), the sum of the barriers between the n-type region and the p-type region on one hand and the metal on the other reaches the magnitude of the band gap, which is approximately 3 eV. In a semiconductor device based on SiC, it is very difficult to obtain a low contact resistance between the semiconductor region and the electrode.